Vacuum-tube circuits



"June 1 VAN METER COUSINS 1,767,954

VACUUM TUBE C IRCUITS Filed June 22, 1929 /NVEN7'0R V. M Cous/Ns ATTDHNEY I Patented June 24, 1930 circuit is not closed.

UNITED. stares YORK v I Application filed June 22,

This invention relates tobnergization of electric space discharge devices.

An object of the invention is to regulate cathode heating current and space discharge current for such devices; d

In one specific aspect the invention is an electric space discharge amplifier having a cathode heating circuit and a plate current supply circuit energized from a power circuit through athree-position switch and a ballast lamp or resistance for maintaining the current supplied by the power circuit constant. When the switch isin its off position the power circuit is open or disconnected from'the heating circuit and the space current circuit. When the switch is operated from its off position to its first operating position the heating circuit is connected to the power circuit through the ballast lamp and a protective resistor, but the space current If the space current circuit were closed in this position of the switch, the potential applied to the plates might be excessive, since the impedances of the space paths are high whenthe cathodes are cold. If the protective resistor were omitted, the heating current might be excessive in this position of the switch, since the ballast lamp tends to maintain its current at a given value corresponding to the proper value of the sum of the heating cur rent and the normal space current, and the space current is zero instead of normal in this position of the switch. When the switch is operated from its first operating posi tion to its other operating position, it closes the space current circuit and short circuits the protective resistor.

The protection of the space discharge de vices in accordance with the invention is of especial utility in the case of uni-potential .VANJ'YIVMETER cousins, on LYNDHURST, NEW JERSEY, AssIGivoR To BELL TELEPHONE LABORATORIES, I1-ICORPORATED,O1 NEW YORK, N. Y.; A CORPORATION OF. NEW

VACUU -T BE oI cUITs 1929. Serial No. 372,933.

The single figure of the drawing shows schematically the specificform of the inven' tionreferred to above.

'The amplifier is a three stage amplifier. The first two stages comprise uni-potential cathodetubes A and A respectively and the third stage comprises two tubes A and A. in push-pull connection. Two tubes R and R are used for rectifying current obtained through 'a voltage step-up transformer 7 from a 110 volt, 60 cycle power supply circuit 10 fed from generator 11. I The rectified current is used to supply the grid and plate potentials for all stages. The currents for heating the filaments of all five of the tubes are alternating currents obtained from power supply circuit 10 through voltage stepdown transformer 12. Thetubes A and A may be, for example, of the heater type disclosed in French Patent 593,321, May 22, 1925, or the type disclosed in U. S. patent to M. J. Kelly, 1,678,145, July 24, 1928.

Waves to be amplified are impressed on input transformer 16 from amplifier input circuit 15. They are transmitted through that transformer to an amplifier input potentiometer or adjustable gain controlling attenuator 20 in theinput circuit oftube A thence throughthat tube and an interstage transformer 21 to an interstage potentiometer 22, and thence through tube A interstage transformer 25, tubes A and A and output transformer 26 to amplifier output circuit 30.

The currents'rectified by tubes R and R pass through a filter 35, comprising inductance coil 36 as a series arm and condensers 37 and 38 as shunt arms, for suppressing voltage and current fluctuations. Points 40 and 41 may be regarded as the positive'and negative output terminals respectively of the filter 35. I

A potential from which-plate potential for tubes A and A is obtained is derived from the junction point 42 of voltage dividing resistances 43 and 44, which are connected across points 40 and 41 by a filter consisting of an inductance coil 45 as a series arm and a condenser 46 as a shunt arm. This filter Thesteady plate current for tubes A and i A passes from the point 40 through a choke coil 56 for suppressing current fluctuations, the primary windings of transformer 26, the tubes A and A the middle pair of secondary windings of the transformer 12, and

' resistances 51 and 52, to the point 41.

resistance.

Negative grid biasing. potential for the tubes A and A is obtained from the voltage drop inresistance 51. The biasing potential for the grid of tube A is applied from the junction of resistances'51 and 52 through a resistance and condenser filter 60 and the secondary winding of transformer 16 and the potentiometer 20. The filter 60 consists of resistances 61 and 62 as series arms and condensers 63 and 64 as shunt arms. 7

The biasing potential for the grid of tube A is applied from the junction of resistances 51 and 52 through a filtering series resistance and shunt condenser 65 and 66 and the secondary winding of transformer 21 and the potentiometer 22.

Negative grid biasing potential for the 1 tubes A and A is obtainedfrom the voltage drop in resistances 51 and 52 The biasing potential is applied from point 41 through a filtering series resistance 68 and shunt condenser 69 and the secondary windings of transformer 25.

Condensers 71 and 72 are the usual stopping condensers, of negligibly low reactance for the frequencies of the wave to be amplified, for blocking passage of direct current.-

Fluctuations of the plate current supply for tube A are further prevented by a filter consisting of the resistances .47 and 48 as series arms and condensers 7 3 and 74 as shunt arms. Fluctuations of the plate current supply for tube A are further prevented by a filter consisting of the resistances 53 and 54 as series arn'cs and condensers 73 and 75 as shunt arms,

The transformers 7 and 1 2 are energized from the circuit 10 through a three position switch and a ballast lamp 81 for regulating the voltage delivered by circuit 10 to maintain that voltage substantially constant.

The ballast lamp may be of the usual t'ype comprisinga; resistance. element having a high positive temperature coefficient of The switch comprises two arcuate conduct-ing plates 85 and 86 insulated from each of the switch the plates 85' and '86 do. not

touch any of the stationary'contacts, and

windings 7 and 12 therefore are disconnected from source 11. In conditioning the amplifier for operation, the filaments are energized byrot-ating the switch to its second position, in which plate 85 connects contacts 7 91 and 92 and plate86 connects contacts 94 and 95, so that transformer 12 is connected to source 11 and lamp 81 through a resistance 98. This resistance prevents the voltage applied to transformer 12 from being so great. as to result in injury to the filaments energized by the transformer; for in this position of the switch the transformer 7 is not drawing current and the current through the ballast lamp is therefore not suflicient to cause the voltage drop in the ballast lamp to have a value substantially as great as when both of the transformers 12 and 7 draw cur rent. To supply plate potential to the tubes, the switch is moved from its second position to its third position, in whichthe resistance 98 is short circuited and both transformers are connected to source 11 through lamp 81.

The delay in the connection of transformer 7 to the source 11 until the cathodes of the regulating means in said circuit, a cathode V energizing circuit for said cathode means, a space current circuit for said electric space discharge means, protective means for said cathode energizing circuit, and means operable to connect said cathode energizing cir cuit to said power supply circuit, said regulating means and said protective means, and at the same time to maintain said space current circuit disconnected from said power supply circuit, and operable also to connect said space current circuit to said power supply circuit and said regulating means and disable said protective means.

2. A wave transmission system comprising electric space discharge means having cathods means, a power supply circuit, a ballast resistance in series in said circuit,- a cathode heating circuit for said cathode means,a heating current transformer'in said'heating cir cuit, a space current circuit for said electric space discharge means, a space current transformer for the latter circuit, a protective resistor for said heating circuit, and a switch having one position in which it disconnects said power supply source from said transformers, a second position in which it disconnects said power supply circuit from said space current transformer but connects said power supply circuit to said heating current transformer with said ballast resistance and said protective resistor in series with said heating current transformer, and a third position in which it short circuits said protective resistor and connects said power supply circuit to-said transformers in parallel, with said ballast resistance in series with the parallel connected transformers.

3. In a circuit for a vacuum tube having cathode and anode, an energizing circuit for supplying cathode heating and space current to said tube, a regulator in said energizing circuit, and a switch movable through different posit-ions in sequence, in one position disabling said energizing circuit, in another position energizing said cathode at no higher than normal operating level and keeping said anode circuit unenergized, and in the next sequential position energizing both said cathode and said anode circuit under control of said regulator.

In witness'whereof, I hereunto subscribe my name this 21st day of June, 1929.

VAN METER COUSINS. 

